EA81 EGT readings

25 posts in this topic

Posted

Hey all, just looking for some input on the following. 

Installed newly rebuilt EA81 with custom manifold and single weber carb. Completed everything and an auto mechanic tuned carb and did 37 degrees advanced timing. Everything sounds great and running smooth. All 4 cylinders firing properly. Connect EGT sensors today and pilot side heats up to 1000 but passenger side not indicating. Idled for 5 minutes and throttled up to 2200rpm for 2 minutes and still nothing. 

Ive swamped sensors and sides of the gauge and those work properly. 

Any advice? 

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Posted

if you have already swapped probes then I am not sure what else to do.  Did you just swap the ends at the gauge or did you swap both probe position and gauge position?

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Posted

if you have already swapped probes then I am not sure what else to do.  Did you just swap the ends at the gauge or did you swap both probe position and gauge position?

yeah I first swapped probes at the gage and it just read properly on the other needle indicating that both sides of the gage worked. I then switched probes to the opposite side and the same side that was reading still read the same with the other probe. 

So am I left to believe the engine perhspd is starving on the one side for fuel but when I remove each plug wire individually the sound and idle changes the exact same when done to each of the 4 

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Posted

After running did you actually feel the exhaust? I know that I've actually had engines that you could put your hand on the exhaust side when something wasn't firing. Although it sounds like it is running smoothly so not sure what to tell you. Which EGT gauge are you running? I've had issues like this before with a Westach. Luckily I had a spare and threw it in. For some reason it fixed the issue even when I had the same results you did after swapping everything around to try to eliminate the probes and gauge. 

Personally when I run into issues like this with an engine I resort to my cheap temp gun to check actual temps. I also tune carbs that way when running dual carbs. At least then I know they are equally starved or rich. 

Good luck, let us know what you end up finding. 

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Posted

Mine does that too ,I'd try 3500 rpm and see what happens, engine isn't really working at idle and low rpm .just my two c@nts

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Posted

I agree with lostman on using a hand held lazer thermometer on the exhausts.  You really should get some reading even if it's low on those cylinders unless they aren't firing at all.  JImChuk

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Posted (edited)

Thanks for the advice guys. Right now my laser thermometer is still Packed somewhere from moving but my mechanic is going to bring one over this weekend. 

Both sides, to the touch are hot beyond being able to touch. The side thats not reading a temp I still had to wait a while before removing the probe (as I look at the burn on my hand). 

The gauge I am using is a westach. I'm going to look at the plugs closer tomorrow to see their colour. I'll also do as suggested with revving up higher. If everything checks out with the laser thermometerer etc then I'll look at trying another gauge. Feels like I'm so close to getting her in the air, yet so far. I explained everything over phone with mechanic and he believes it's taking a while to get that reading because his tests with compression and vacuum etc all looked perfect. 

Thans again everyone I'll keep posting with what happens

Edited by fusionfab

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Posted

Well if you burned your hand on the exhaust, it must be running on that  cylinder.  It's always a good idea to look at the plugs, they will tell the story for sure.  JImChuk

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Posted (edited)

 Soob EA81 exhausts both cylinders on a side thru a single port, so you should have gotten some kind of reading if it was that hot.   What is the lowest temperature on your gauge?  I have heard of this mystery problem with Westach  gauges.   One other thing you could try is unplugging the working lead from the gauge and see if the dead side will then give you a reading - possibly they are fighting or crossing each other inside the gauge?  These are very small signals.  EDMO

Edited by EDMO

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Posted (edited)

 Soob EA81 exhausts both cylinders on a side thru a single port, so you should have gotten some kind of reading if it was that hot.   What is the lowest temperature on your gauge?  I have heard of this mystery problem with Westach  gauges.   One other thing you could try is unplugging the working lead from the gauge and see if the dead side will then give you a reading - possibly they are fighting or crossing each other inside the gauge?  These are very small signals.  EDMO

I'm hoping it's a gauge problem. The lowest temp is 800F and wasn't moving. I tried unplugging the side that's reading and still nothing. 

im also going to try a trick with the acetylene and see if it changes.

maybe one side is hogging the fuel?

Edited by fusionfab

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Posted

Not sure what you mean about the acetylene, but maybe you are thinking about heating up the probes with a torch.  That will tell you if the gauge is working.  I would use a propane torch though,  Acetylene might be to hot.  JimChuk

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Posted

Not sure what you mean about the acetylene, but maybe you are thinking about heating up the probes with a torch.  That will tell you if the gauge is working.  I would use a propane torch though,  Acetylene might be to hot.  JimChuk

with the acetylene you just turn the gas on without igniting and place the torch, to start, by the air filter. If carb isn't delivering enough fuel you'll hear the idle smooth right out and run even. It's what I do for multiple carb applications if the engine is running rough. Place it by each carbs intake side and it'll change the idle when you've located the carb not delivering fuel. 

It also works for vaccuum leaks to move the torch around the intake manifold and the engine wound will change if you've passed it by a leak. 

Now, my engine doesn't sound rough at all and runs smoothly but going to see if temps go up on the gauge when I move the torch around. We'll see

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Posted

Another thought: Are the probes the same distance from the head? even a couple inches different may allow the exhaust to cool just enough to vary the reading. I know it's a long shot but I'm trying to think of other things you can check. 

 

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Posted (edited)

Another thought: Are the probes the same distance from the head? even a couple inches different may allow the exhaust to cool just enough to vary the reading. I know it's a long shot but I'm trying to think of other things you can check. 

 

Yes, the side I am having issues with is in fact lower on the pipe/further from the head by about 1-1/2 to 2". I just went and picked up another thermometer and each side while at 1000rpm idle is heating up relatively close. The pipe temp, and measured in similar locations are only differing about 30F degrees from each other and are alternating up and down. Brought up to 3000 rpm for a few seconds and both pipes equally were around the 475F mark steady and equally rising before idling down, differing only 5-15F degrees 

But still confused as to why the tach will only pick up the one side, even after switching sides on the tach, so I will try removing one of the probes, tig welding the hole closed and try to match them. 

I did in fact notice that if I moved the laser from the thermo down even a few inches on the pipe, the temp would drop over 100 degrees. My guess (lostman)just as you suggested, that may be the issue. I will tinker with that this afternoon an try and get the probes equal distance from the heads. 

 

Thanks again everyone. 

Edited by fusionfab

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Posted (edited)

I believe that the probes should be located about 2.5" from the flange on the pipe?  The cars didn't have them. 

I haven't planned to put them on mine, since I have no way to lean my 2-brl Holly and don't have an IFA prop.   EDMO

Edited by EDMO

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Posted

Just tried moving the probes and they are pretty much dead even with each other. at 3000 rpm directly at the probes the pipe measures 450-465F degrees from the infrared thermo. Starting think now the gauge is to blame. Also by the pulling the plugs after each running, the front passenger side is clear and lightly brown, and the rear passenger side is lightly black/carbon. So going to maybe try adjusting the valves...again and see. Trying to eliminate all options before either calling Westach or ordering a new gauge.

 

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Posted (edited)

You say you have a custom intake manifold?  Could that be part of the problem of rich on rear cylinder, lean on front?  EDMO

Edited by EDMO

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Posted

You say you have a custom intake manifold?  Could that be part of the problem of rich on rear cylinder, lean on front?  EDMO

Yeah I had custom made this one because the stock one wouldn't fit with starter location. so this one is all aluminum and 1-3/8" ID and all welds ground smooth internally. But it just feeds the two sides, not each individually. I'll attach a pic. 

I checked WESTACH site and under their troubleshooting they have the Gauge resistance should read between 8-20 ohms and the needle should move when doing this. I checked both sides on gauge and both read 9 ohms but needles don't move when doing this. The thermocouples should read around 2.5 ohms. Both bounce between 2 and 3 ohms after checking. I am running out of options aside from the needles not moving on gauge when checking their resistance.

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Posted

Here's the manifold, after I finished it I had it leak tested and the flanges and carb surface machined

IMG_5560.JPG

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Posted

Guess your plane is sitting on the tail - could this make the rear run richer?  EDMO

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Posted

Yeah she's a TD but not sure if that's why rear is running richer. Going to go through those plug colour charts 

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Posted

So an update on this thread. I messed around with the thermocouples tonight switching them from side to side. It appeared one side was registering so I switched the wires from that side on the gauge end and now the other half of gauge was reading that same side. Both sides worked individually. Switched thermocouples and both worked on the same side. Confused as all hell I initiated the highly sought after and old fashioned knuckle tap on the gauge and suddenly both sides started working together. Running at even temps. One side cools faster when idling down. Going to let engine cool and will test again. 

So guessing a thermocouple is maybe going bad which i'm not certain of because they both measure the exact same resistance. Or maybe something with the gauge. We'll see I guess....OR its just fixed itself now.

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Posted

So an update on this thread. I messed around with the thermocouples tonight switching them from side to side. It appeared one side was registering so I switched the wires from that side on the gauge end and now the other half of gauge was reading that same side. Both sides worked individually. Switched thermocouples and both worked on the same side. Confused as all hell I initiated the highly sought after and old fashioned knuckle tap on the gauge and suddenly both sides started working together. Running at even temps. One side cools faster when idling down. Going to let engine cool and will test again. 

So guessing a thermocouple is maybe going bad which i'm not certain of because they both measure the exact same resistance. Or maybe something with the gauge. We'll see I guess....OR its just fixed itself now.

Sounds like you had a gauge problem - not thermocouple.  ???  EDMO

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Posted

So an update on this thread. I messed around with the thermocouples tonight switching them from side to side. It appeared one side was registering so I switched the wires from that side on the gauge end and now the other half of gauge was reading that same side. Both sides worked individually. Switched thermocouples and both worked on the same side. Confused as all hell I initiated the highly sought after and old fashioned knuckle tap on the gauge and suddenly both sides started working together. Running at even temps. One side cools faster when idling down. Going to let engine cool and will test again. 

So guessing a thermocouple is maybe going bad which i'm not certain of because they both measure the exact same resistance. Or maybe something with the gauge. We'll see I guess....OR its just fixed itself now.

Sounds like you had a gauge problem - not thermocouple.  ???  EDMO

I was thinking the same thing EDMO, I only have a few things left to do but will have plenty of run ups and taxiing before any air time. So hopefully if theres an issue with it, it tells me sooner than later. Both side of the gauge were reading same resistance. 

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Posted

So an update on this thread. I messed around with the thermocouples tonight switching them from side to side. It appeared one side was registering so I switched the wires from that side on the gauge end and now the other half of gauge was reading that same side. Both sides worked individually. Switched thermocouples and both worked on the same side. Confused as all hell I initiated the highly sought after and old fashioned knuckle tap on the gauge and suddenly both sides started working together. Running at even temps. One side cools faster when idling down. Going to let engine cool and will test again. 

So guessing a thermocouple is maybe going bad which i'm not certain of because they both measure the exact same resistance. Or maybe something with the gauge. We'll see I guess....OR its just fixed itself now.

Sounds like you had a gauge problem - not thermocouple.  ???  EDMO

I was thinking the same thing EDMO, I only have a few things left to do but will have plenty of run ups and taxiing before any air time. So hopefully if theres an issue with it, it tells me sooner than later. Both side of the gauge were reading same resistance. 

Well, if a knuckle tap got it to working, and it gives you trouble, a hammer tap will get you a new gauge!~  EDMO

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